Indie games often cater to whatever the devs found fun as kids, that kind of creates it's own kind of stagnation.

The indie boom of the late 00s and early 10s was to a certain degree the result of odd creatives working the Flashgame community (cut-throat in itself) being forced out onto other platforms as it died combined with other platforms providing monetization possibilities.

As with everything, once there was money to be found the vultures moved in.